The leadership of South Vietnam were Catholics that had been installed by the French who were predominately Catholics themselves.
President Kennedy our first Catholic president was a close friend of Archbishop Hannon who visited the White House many times.
Some people think, including me, that Pres. Kennedy was directed by the Vatican/Pope during his numerous meetings with the Archbishop, to help their fellow Catholics in South Vietnam.
Its never been proven that's why the U.S. got involved in Vietnam.
But it sounds reasonable to me. ...